A lectin-histochemical study on microglial
development has been performed on the rat central nervous system. Isolectin B4
from the Griffonia simplicifolia (GSA I-B4) and Ricinus communis
agglutinin-120 (RCA-1) were used as labelling lectins. Our results demonstrate
the existence of microglial elements in the nervous parenchyma at E18, derived
from the meningeal connective tissue layer. Later, another microglial source
became evident, namely the cavum septum pellucidum, which serves for entrance
of microglia pervading the supraventricular corpus callosum and the
subependyma of the lateral ventricles. From P12 onwards, the microglial
sources became inactive.

The development of microglial cells in the
postnatal rat retina is described using histochemical techniques for acid
phosphatase and peroxidase as well as silver impregnations for microglia. On
the second postnatal day, round acid phosphatase-positive macrophages appeared
on the vitreal surface of retina, locating themselves close to developing
blood vessels. Later, microglial precursors invaded retinal tissues, reaching
the outer plexiform layer by the tenth postnatal day. In all stages studied,
microglia or their precursors were peroxidase-negative. The transformation of
round microglial precursors into adult ramified microglia is also described.
Owing to the relation found between developing microglia and blood vessels, a
vascular origin is proposed for the retinal microglial cells.

The immunohistochemical detection of
bromodeoxyuridine (BrdU) was used to study the cell proliferation in the
developing rat pineal gland, from the appearance of pineal primordium in the
embryonic day 15 (E15) until 30 days after birth. The results showed three
different proliferative phases. From E15 to E21, the pineal gland shows a
phase of rapid proliferation. The second phase corresponds to the first
postnatal week, in which the number of labeled cells per surface unit
decreases suddenly to values between 20% to 10% of those of embryonic period.
From the second postnatal week onwards, the number of BrdU-positive cells
progressively decreases.

The immunohistochemical expression of glial
fibrillary acidic protein (GFAP) and vimentin (VIM) was studied in reactive
astrocytes of the rat cerebral cortex 5 days after a brain injury. Seriated
Epon semithin sections were immunostained alternatively for GFAP or VIM.
Thereafter, both antigens were detected in consecutive sections of the same
cell. Bordering the wound, an inner reactive glial layer 300-350 microns
thick, showed positive astrocytes with the two immunohistochemical techniques.
In this layer, about 60% of the GFAP positive astrocytes were also positive
for VIM. Outside the inner layer, only GFAP positive astrocytes could be
found.

The localization of vimentin (VIM) and glial
fibrillary acidic protein (GFAP) was studied immunohistochemically in adult
rat optic nerve. Consecutive Epon semithin tissue sections were immunostained
respectively for VIM or GFAP. With this method, both antigens were detected in
consecutive sections of the same cell. According to our results, most
astrocytes in the adult rat optic nerve showed coexpression of VIM and
GFAP.

In the present work, coexpression of vimentin
(VIM) and glial fibrillary acidic protein (GFAP) is demonstrated in the glial
cells of the adult rat pineal gland. Serial consecutive Epon semithin sections
(0.5 microns thick) were alternately immunostained for VIM and GFAP. GFAP
positive cells and processes were found in the proximal region of the pineal
gland, near the pineal stalk. Most of these cells were also immunostained for
VIM in adjacent semithin sections. The significance of the coexpression
VIM-GFAP and the restricted location of GFAP positive cells is discussed in
relation with the maturation of pineal glial cells.

The innervation of the pineal gland has been
studied during the embryonic development and the first 10 days after hatching.
On day 17 of embryonic development, the first nerve fibers are observed in the
pineal capsule. They appear at the stalk level and rise to locate mostly on
the anterior side of the capsule. Some nerve fibers leave these nerve bundles
to penetrate the gland and they situate in the connective septa (18 days of
development). From day 19 of development onwards, nerve fibers locate only in
the parafollicular layer. Cells that may be identified as neurons are found in
the pineal parenchyma.

A study of the embryonic development of the
pineal gland of the chicken was performed with the optical microscope. The
time of apparition of the first outline, as a derivative of the roof of the
third ventricle, was fixed at 3 days. The major portion of the pineal
parenchyma is derived from the frontal wall of the outline. All the vesicles
and follicles were formed by solid mammilliform projections which subsequently
presented a central lumen. In no case was a communication of the follicular
cavities with the pineal recess observed. Three categories of vesicles or
follicles can be distinguished according to their origin.

The embryonic development of the albino rat
pineal gland has been studied from day 13 of development until birth. The
first pineal anlage appears as a midline evagination of the diencephalic roof,
which soon adopts a tubular morphology. At 17 days, the disappearance of the
pineal recess begins, along with the transformation of the gland into a solid
organ. The latter is mainly achieved by an infolding and thickening of the
dorsal recess wall, from which derives most of the future pineal parenchyma.
Blood vessels are mainly derived from the vessels found in the dorsal surface
of the pineal gland.

The acid phosphatase reaction, applied to light
and electron microscopy, was studied in the chicken pineal gland from the
moment of hatching until 2 months of age. From the moment of hatching there is
a great amount of acid phosphatase, which is mainly found in the vicinity of
the lumen of both the recess and large follicles. Acid phosphatase is poor in
the parafollicular layer. From day 30 onwards, there is an obvious
fragmentation of the recess and of large follicles. Also, the parafollicular
layer differentiates to form new follicles. The dense polymorphous bodies of
the B pinealocytes are ultrastructurally identified as lysosomes.

The structural pattern of the pineal gland in
the hen corresponds to a more advanced stage of the evolution which began in
an early period of the animal's life. This evolution corresponds mainly to the
transformation of the large follicular cavities into cellular 'rosettes'. The
parafollicular layer disappears from the rosette wall which thus remains with
only one row of cells (A and B pinealocytes). The cellular hypertrophy and the
great development of the pinealocyte organelles in the adult pineal gland
makes us think of this gland as a functionally active organ. This functional
activity must have remained during the entire period of the time studied (1--5
years), due to the ultrastructural uniformity found and due to the fact that
we could not observe any type of degenerative process in the
gland.

The immunocytochemical localization of basic
fibroblast growth factor (b-FGF) during the postnatal development of the rat
pineal gland was studied using a polyclonal antibody against the fraction 1-24
of bovine recombinant b-FGF. Basic FGF immunoreactivity was evident from day
20 after birth in the endothelial cells and perivascular spaces of the gland.
Although b-FGF immunostaining showed its maximal expression at 30-45 days, it
was maintained throughout the entire study period (up to 6 months), mainly in
the distal zone of the gland. Pinealocytes did not show b-FGF immunoreactivity
at any time. There were no differences in the localization patterns or the
intensity of b-FGF immunostaining after the prenatal denervation with DSP-4, a
neurotoxic amine. The physiological role of b-FGF in the adult pineal gland
remains unknown; however, it does not seem to play a major role during the
cytodifferentiation period of the parenchymal cells, or during the
neovascularization in the early postnatal days. Furthermore, its
immunocytochemical expression is not affected by the prenatal sympathetic
denervation with DSP-4, in contrast with other neurotropic
factors.

In the present work, the presence and
distribution of astrocytes in the rat pineal stalk is investigated applying an
immunohistochemical technique for the demonstration of glial fibrillary acidic
protein (GFAP) on Epon-embedded semithin sections (0.5 micron thick).
GFAP-immunoreactive cells are evenly and regularly distributed along the
entire pineal stalk. The GFAP-immunoreactive cells display a stellate shape
showing variable numbers of cell processes that are mainly oriented parallel
to the longitudinal stalk axis. Astrocytic processes show a clear tendency to
encircle the remaining elements of the pineal stalk; i.e., pinealocytes, nerve
fibres and blood vessels. Furthermore, glial processes form a cover layer
separating the stalk from surrounding anatomical structures.

Sympathetic nerve fibers arising from the
superior cervical ganglia are the main innervation of the rat pineal gland.
Since most organs innervated by these ganglia contain nerve growth factor
(NGF), the hypothetical existence of NGF in the pineal gland was investigated.
The peroxidase anti-peroxidase technique was applied for the
immunohistochemical demonstration of NGF using a polyclonal antiserum on
Bouin-fixed, paraffin-embedded pineal glands from adult, young and
6-hydroxydopamine (6-OHDA)-treated rats. Few immunopositive cells were
observed in the adult pineal gland. A more conspicuous population of
immunoreactive cells was noted in young animals (20-45 days old), especially
in those chemically denervated with 6-OHDA. NGF immunoreactive cells displayed
a stellate shape resembling the interstitial or glial cells previously
described in the rat pineal gland. Since NGF plays a trophic effect on
sympathetic neurons during development and adulthood, we postulate that its
presence in the pineal gland may exert a trophic role on its sympathetic
innervation.

The expression of glial antigens vimentin (VIM)
and glial fibrillary acidic protein (GFAP) is described in the pineal gland of
cats and dogs from the first postnatal days to adulthood. VIM immunopositive
cells were observed from the first postnatal days in both species. GFAP
expression starts from the second postnatal week. In adults, a notable
population of stellate cells immunopositive for GFAP and VIM was found
dispersed throughout the gland. According to their immunocytochemical profile,
these cells could be identified as astrocytes.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=8229641&lang=es&site=ehost-live">Immunohistochemical
study of the pineal astrocytes in the postnatal development of the cat and dog
pineal gland.</A>

Base de datos:

MEDLINE

Registro: 23

Título:

Immunohistochemical study of the pineal glial
cells in the postnatal development of the rat pineal gland.

Autores:

Borregón A; Boya J; Calvo JL; López-Muñoz
F

Dirección del autor:

Department of Histology, Faculty of Medicine,
University Complutense, Madrid, Spain.

The developmental expression of the glial
antigens, vimentin (VIM), glial fibrillary acidic protein (GFAP), and S-100
protein is described in the rat pineal gland from the first postnatal day to
adulthood. Thick VIM immunopositive cell cords forming a network throughout
the pineal gland were observed from the first postnatal days. These cords
progressively disappeared during the first postnatal month as their cells
dispersed into the pineal parenchyma. From 20 to 25 postnatal days, pineal
glial cells appeared as isolated star-shaped VIM immunopositive cells.
Immunostaining for GFAP and S-100 protein showed a similar developmental
expression pattern. Both antigens appeared later than VIM (15-20 postnatal
days) and were restricted to the pineal glial cells located in the proximal
third of the gland, close to the pineal stalk.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=8320635&lang=es&site=ehost-live">Immunohistochemical
study of the pineal glial cells in the postnatal development of the rat pineal
gland.</A>

Base de datos:

MEDLINE

Registro: 24

Título:

Influence of the light and dark phase of the
cycle on the cellular proliferation in the pineal gland of the adult rat: a
bromodeoxyuridine immunohistochemical study.

The cellular proliferative activity in the adult
rat pineal gland was studied using bromodeoxyuridine immunohistochemistry
during the light and dark phases of an artificial 12L:12D photoperiod. The
results showed statistically significant differences in the number of labeled
cells between the light and dark phases, with the labeled cells being almost
threefold more abundant in the light period. Minor changes were also found in
the pineal gland volume between both periods. The decrease in the number of
labeled cells in the dark phase of the cycle could be related to the
well-documented antimitotic action of melatonin.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=9379340&lang=es&site=ehost-live">Influence
of the light and dark phase of the cycle on the cellular proliferation in the
pineal gland of the adult rat: a bromodeoxyuridine immunohistochemical
study.</A>

Base de datos:

MEDLINE

Registro: 25

Título:

Microglial cells in the central nervous system
of the rabbit and rat: cytochemical identification using two different
lectins.

Autores:

Boya J; Carbonell AL; Calvo JL; Borregon
A

Dirección del autor:

Department of Histology and General Embryology,
Faculty of Medicine, University Complutense, Madrid, Spain.

Microglial cells were selectively demonstrated
in the central nervous system of adult rabbits and rats using lectin
histochemistry. Biotinylated Ricinus communis agglutinin-120 (RCA-1) and
biotinylated Griffonia simplicifolia B4 isolectin (GSA I-B4) were used as
histochemical markers on sections of Bouin-fixed paraffin-embedded cerebrum
and cerebellum. Results were quite similar using both lectins and both
species. GSA I-B4 resulted in a better staining in the rat, while RCA-1
labelling was superior in the rabbit. Neither neurons nor glial cells other
than microglia were stained with our technique. Lectin histochemistry applied
for the detection of microglial cells appears to be of sufficient selectivity
and may be considered as an important tool in the morphological and
neurobiological study of these cells.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=1867066&lang=es&site=ehost-live">Microglial
cells in the central nervous system of the rabbit and rat: cytochemical
identification using two different lectins.</A>

The nature of phagocytes appearing in lesions of
the central nervous system is strongly debated with a tendency to assess an
exclusively hematogenous origin. We studied the origin of phagocytes appearing
in a stab wound in the rat brain. Histochemical stains for acid phosphatase
and peroxidase, and silver impregnation techniques were used for our study.
The results obtained showed the existence of two macrophage types: endogenous
microgliocytes and exogenous monocytes.

The present study shows the existence of
oxytalan fibres in the connective tissue spaces of the rat pineal gland. The
identification of these fibres with light microscopy is based on their ability
to stain with aldehyde-fuchsin and orcein after oxidation with peracetic acid.
Using the electron microscope, oxytalan fibres appear as bundles of fibrils of
12-15 nm without transverse striation. Oxytalan fibres increase with age,
being most abundant in the old rat.

The authors studied the evolution of the pineal
gland of the chicken (Gallus gallus) from hatching until 34 months of age.
They describe the progressive decrease of the follicular cavities and the
appearance of solid-looking cavities. The stroma increases with age, dividing
the pineal parenchyma into territories of small caliber.

The morphological development of the rat pineal
gland has been studied from 1 to 60 days of age. During the first days,
undifferentiated cells (pinealoblasts) with scanty cytoplasm and frequent
mitotic figures were observed. The differentiation of cell types (Types I and
II pinealocytes) began on the third day after birth and was completed by days
15-20. At 3 days of age, nerve fibres were first observed, both in the
connective spaces and in the parenchyma. After 5 days, an important
hypertrophy of pinealocytes began, mostly Type I, which continued until 60
days of age. After 45 days, all the ultrastructural features described in the
adult pineal gland were already present. The findings are
discussed.

The light microscopical morphology of the dog
pineal gland from the first postnatal day to maturity is described. In the
first postnatal week, the pineal parenchyma shows immature cells and many
mitotic figures. In this week, pigmented cells are observed for the first
time, both in the pineal gland and in extrapineal nodules. Throughout the
second week, the pineal parenchyma shows a cordonal pattern that disappears
progressively in the following stages. From the 20-30th day onward, it is
feasible to discern the cell types characteristic for the adult pineal gland.
In the adult animals, the length of the pineal gland axes almost quadruplies
that of the pineal gland in neonatal stages. The light microscopical features
of the adult dog pineal gland are also described.

The ultrastructure of the dog pineal gland from
the first postnatal day to the seventh month is described. In the first
postnatal stages, pineal parenchyma only shows immature proliferative cells
with abundant cytoplasmic glycogen. Nerve fibers are seen in the pineal
connective tissue spaces. The differentiation of the dog pineal cell types
begins in the first postnatal week. Both pinealocytes and pigmented cells are
first seen on the fourth postnatal day. The pineal astrocytes are observed on
the tenth day. Immature cells are still found in the pineal gland of 1 mo-old
dogs. The differentiation of the dog pineal cell types is completed by the
second postnatal month.

The postnatal development and morphology of the
adult albino rat pineal gland was studied from one day up to ten months of
age. During postnatal life there was a marked increase in gland and
pinealocyte volume, more intense during the first 45 days. After ten days, the
differences in nuclear morphology of parenchymal cells showed two different
types of pinealocyte. The characteristic adult arrangement of pinealocytes in
cords and pseudo-rosettes was observed after 15-20 days. After 75 days there
was a progressive increase in the number of connective tissue
fibres.

Immunoperoxidase methods for the demonstration
of three glial antigens, vimentin, glial fibrillary acidic protein, and S-100
protein, were applied to routine-fixed paraffin sections of rat pineal gland.
A pre-embedding electron microscope immunoperoxidase method was also used to
study the ultrastructural localization of S-100 protein in pineal cells. Light
and electron microscopic results showed the presence of these antigenic glial
markers in the second pineal cell type. The term glial cell is proposed for
the second of parenchymatous cell in rat pineal gland.

Light- and electron-microscopic features of
pigmented cells in the cat pineal gland are described. These cells were
observed throughout postnatal life from the second postnatal day to the oldest
cats studied (up to 13 years old). No apparent relationship was observed among
the amount of pigment and the animal age or sex. Pigmented cells showed a
preferential localization at the ventral surface of the pineal gland near its
distal end. The pineal pigment was histochemically identified as melanin.
Pineal pigment granules showed ultrastructural features similar to melanocyte
melanin granules.

By means of teledischarge techniques from the
database MEDLINE we selected those documents that contained in their title one
or several of the following descriptors: pineal*, epiphys*, or melatonin*, in
addition to the descriptor pineal-body in the MESH (Medical Subject Headings)
section. A total of 7,617 original documents published between 1966 and 1994
were extracted that dealt with any aspect related with the pineal gland or its
main secretary product, melatonin. The main bibliometric laws were applied:
Price's Law on the increase in scientific literature, Bradford's Law on the
dispersion of the scientific literature, and Lotka's Law on the author's
productivity. Furthermore, we have analyzed the participation index (PaI) of
the main countries within the global production, the productivity index of the
authors (PI), and the number of authors/paper index. Our results demonstrate
an exponential increase of the scientific literature on the pineal gland ("r"
value = 0.983, in contrast with a "r" value = 0.966 after the linear
adjustment). The number of publications on melatonin was less than those on
other aspects of pineal research until 1991, when this situation was reversed.
The journal with the largest number of original papers is Journal of Pineal
Research (1st Bradford's zone) with 533 articles, followed by Journal of
Neural Transmission (258) and Neuroendocrinology (221), which constituted the
2nd Bradford's zone. The total number of authors is 9,140, responsible for
23,524 authorships. 3.8% of the authors present a PI > or = 1 (large
producers), and 64.9% a PI = 0 (occasional authors). Lotka's Law was widely
fulfilled in this material since 10.3% of the authors are responsible of 50.2%
of all the papers. The average number of authors per paper has changed from
2.29 in 1966 to 3.85 in 1994. The most productive country (during the interval
between 1988-1994) was USA (PaI = 30.6), followed by Japan (7.15), United
Kingdom (6.45), Germany (6.37), France (6.26), Italy (6.15) and Spain (5.34).
Of the total number articles published, 86.9% are in English.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=8797178&lang=es&site=ehost-live">Scientific
research on the pineal gland and melatonin: a bibliometric study for the
period 1966-1994.</A>

Base de datos:

MEDLINE

Registro: 36

Título:

Sex-related differences in the nuclear
population of postpubertal rat pineal gland. A quantitative study.

Autores:

López-Muñoz F; Boya J; Calvo JL

Dirección del autor:

Department of Histology, Faculty of Medicine,
University Complutense, Madrid, Spain.

Male and female parenchymal pineal cell types
have been studied throughout postpubertal development to determine the
existence of sex-related differences on a time basis. Six age groups (2, 3, 4,
8, 15 and 24 months) of eight rats (4 males and 4 females) were used in this
study. Nuclei of both parenchymal pineal cell types were counted in 5 areas of
26.377 microns 2 per pineal gland on semithin sections. Nonparametric
statistics of our results (Mann-Whitney U-test and Kruskal-Wallis H-test)
demonstrated significant differences between male and female pinealocytes
through the stages studied. In all age groups, the number of nuclei per unit
area was larger in female rats. Pineoglial cells did not show significant
sex-related differences.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=1804426&lang=es&site=ehost-live">Sex-related
differences in the nuclear population of postpubertal rat pineal gland. A
quantitative study.</A>

The pineal gland of rats 12-28 months old was
studied with light and electron microscopes. All pineal components exhibited
regressive changes of different intensity with age. In type I pinealocytes,
there was a marked increase in dense bodies as well as the occasional
appearance of wide cell profiles full of vesicles. Type II pinealocytes showed
nuclear infoldings and cytoplasmic deposits of lipofuscin. Pineal stroma
displayed an increase in connective tissue fibers, both collagen and oxytalan,
as well as remains of basement membranes and other materials of unknown
nature. Calcareous concretions were also found, mostly in the pineal capsule.
All regressive changes were more intense with increasing age.

The light and electron microscopic features of
pigmented cells in the adult dog pineal gland have been described. The
presence of pigmented cells was a constant characteristic of the dog pineal
gland, though wide variations in the amount of pigment could be found among
different animals. Conversely, the localisation of pigmented cells was very
constant on the basal surface of the proximal region of the pineal gland.
Frequently, clusters of pigmented cells were seen in the posterior commissure
and the neighbour meningeal spaces, near the pigmented pineal zone. The pineal
pigment has been identified as melanin according to its morphological features
and histochemical properties. Several types of granules were identified
ultrastructurally, apparently corresponding to different stages of a
maturation process. The pigmented cells were identified as a special type of
pinealocyte according to their ultrastructural features.

The ultrastructure of the pineal gland in the
adult cat is described and compared with that of other mammals. Connective
tissue spaces showed capillaries with nonfenestrated endothelia and numerous
unmyelinated nerve fibers. In the proximal region of the gland, myelinated
nerve fibers coming from the anterior commissure were also found. Cat
pinealocytes showed a nucleus with prominent nucleoli, a well developed Golgi
apparatus, centrioles, granular endoplasmic reticulum, ribosomes, abundant
microtubuli and enlarged mitochondria. Pinealocytes showed several long
processes with bulbous endings filled with clear vesicles and scarce
"synaptic" ribbons. Pineal astrocytes and their processes were characterized
by the presence of abundant filaments.

The pineal gland of chicks treated with
oestrogens and androgens has been studied histochemically and
ultrastructurally from post-hatching until 90 days of age. The results
obtained may demonstrate a precocious maturity of the gland caused by its
response to the early high level of sex hormones circulating in the
blood.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=7462093&lang=es&site=ehost-live">The
influence of sex hormones on the pineal gland of the chick: a histochemical
and ultrastructural study.</A>

The rat brain has been studied between 6 hours
after birth and 100 days, using histochemical techniques for acid phosphatase
and peroxidase, and silver impregnation for microglial cells. The results
indicate that microglia come initially from acid phosphatase-positive cells of
the meninges. These invade the nervous parenchyma and transform into ramified
microglia. At 3 days of age similar cells are present on the outer surface of
the large blood vessels, from which site they migrate into the nervous
parenchyma. In 100 days old rats the acid phosphatase-positive cells are
practically all pericytes. None of the microglial cells or their precursors
give a positive reaction for peroxidase.

The present ultrastructural study demonstrates
the presence of oxytalan fibres in normal and regenerating leptomeninges of
adult albino rats. They appear as bundles of fibrils 10-15 nm thick without
transverse striations, which frequently merge with collagen
microfibrils.

The immunohistochemical detection of
bromodeoxyuridine (BrdU) was used to study the time of origin of the cells in
the pineal gland of the rat. A study was made involving 17 groups of 4 rats
each, administered with a single dose of bromodeoxyuridine (BrdU, 25 mg/kg) in
7 phases of the embryonic period (E15 to E21) and in 10 postnatal phases
(between P0 and P30), followed by determination in each rat of the number of
visible immune-labeled cells in the pineal gland 60 days after birth. The
results show that approximately 60% of the pineal cells underwent the last
division(s) prior to differentiation in the prenatal period between E18 and
E21. The rest of the pineal cells originated after birth, particularly in the
first 5 postnatal days.

Ultrastructural changes in the rat pineal gland
were studied quantitatively 7 and 60 days after the sympathetic denervation by
bilateral excission or decentralization of superior cervical ganglia. The
surface occupied by pineal parenchymal cells decreased in rats of experimental
groups with respect to the control group. Furthermore, profile areas of the
cytoplasm, nucleus and nucleolus of the pinealocytes were also diminished.
Cytoplasmic lipid droplets in the pinealocytes were markedly decreased in
number and size in experimental rats. As demonstrated by the Kruskal-Wallis H
test, statistically significant differences were found between rats of the
control and operated groups. Rats treated by superior cervical ganglionectomy
or decentralization showed morphological changes indicating a hypofunctional
pineal gland, although differences were found between both groups.

The ultrastructure of the albino rat embryo
pineal gland was studied from day 13 of development through birth. In the
first stages (13-16.5 days of development) the pineal evagination presents a
barely differentiated epithelium. From 17 days onward the transformation of
the pineal gland from a tubular evagination into a compact organ occurs. The
obliteration of the recess takes place by means of two mechanisms: (a)
multiple foldings of the epithelium which determine an approximation and
fusion of the walls of the recess, and (b) occupation of the lumen by cells
extruded from the pineal epithelium. Embryos of 18-21 days of gestation still
show remains of the pineal recess. From day 16.5 onward elements of the pineal
parenchyma have been found outside the pineal epithelium contour. They contact
with the mesenchymal cells without a basal lamina separating both elements.
Day 20 marks the beginning of recognizable differentiation of pineal cellular
types. However, in the newborn rat these types are not yet clearly
established.

The authors studied the embryonic development of
the pineal gland of the chicken with the electron microscope. The denomination
of 'pinealoblasts' was given to the undifferentiated cells which form the
primitive pineal outline. In the wall of the pineal cavities, the follicular
and parafollicular zones were distinguished; these are formed by type A and
type B pinealocytes, the B type being much more abundant. The degenerated
cells are constant in the pineal throughout its embryonic development, but
much more abundant in the early phases.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=425823&lang=es&site=ehost-live">Ultrastructural
study of the embryonic development of the pineal gland of the chicken (Gallus
gallus).</A>

Base de datos:

MEDLINE

Registro: 47

Título:

Ultrastructural study of the neuroglial and
macrophagic reaction in Wallerian degeneration of the adult rat optic
nerve.

Autores:

Carbonell AL; Boya J; Calvo JL; Marin
JF

Dirección del autor:

Department of Histology and General Embryology,
Faculty of Medicine, Complutense University, Madrid, Spain.

The Wallerian degeneration of the optic nerve of
adult rat has been studied after destroying the retina. Animals were
sacrificed between 4 days and 1 year after the lesion. Different cell types of
the optic nerve have been studied ultrastructurally. Our results demonstrate
the existence of a population of macrophages, probably of microglial origin,
responsible for scavenging degenerated myelin. Astrocytes suffer a process of
proliferation and hypertrophy, and are massively stuffed by gliofilaments,
leading to a glial scar. These cells apparently do not participate in
phagocytic phenomena, while some cytoplasmic inclusions (e.g. lipid droplets)
suggest some implication in the local metabolization of some tissue
degradation products. Oligodendrocytes do not undergo ultrastructural changes,
showing a rather quiescent appearance.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=1804422&lang=es&site=ehost-live">Ultrastructural
study of the neuroglial and macrophagic reaction in Wallerian degeneration of
the adult rat optic nerve.</A>

Base de datos:

MEDLINE

Registro: 48

Título:

Ultrastructural study of the post-hatching
evolution of the pineal gland of the chicken (Gallus gallus).

There is a marked evolution in the
ultrastructure of the chicken pineal gland after hatching. The typical large
follicular cavities that are visible just after hatching disappear with age,
giving the pineal a large number of small-caliber cavities which are
practically filled by the prolongations of the pinealocytes. This gives the
organ an apparently solid aspect. There are still two large cell types in the
follicular wall: the A and B pinealocytes, with the B type being considerably
more abundant.

<A
href="http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=7405520&lang=es&site=ehost-live">Ultrastructural
study of the post-hatching evolution of the pineal gland of the chicken
(Gallus gallus).</A>

Base de datos:

MEDLINE

Registro: 49

Título:

Ultrastructural study on the origin of rat
microglia cells.

Autores:

Boya J; Carbonell AL; Calvo J; Borregón
A

Dirección del autor:

Department of Histology, Faculty of Medicine,
University Complutense, Madrid, Spain.

An ultrastructural study of the origin of
microglial cells has been performed in albino rat brains taken from 17-day-old
embryos up to 35-day-old rats. Invasion of the nervous parenchyma by
macrophagic cells which appear in mesodermal sources is described. Although
the two main microglial sources are the meningeal membranes and the vascular
adventitia, pericytes may also participate in the formation of microglial
cells.

The ultrastructure of the rat pineal gland was
studied from 75 days until 10 months of age. Type I pinealocytes of young
adults showed nuclei with dispersed chromatin, numerous infoldings of the
nuclear envelope and well developed nucleoli. The cytoplasm displayed many
mitochondria and clusters of smooth endoplasmic reticulum. With increasing
age, there was a clear increase in the number of dense bodies or lysosomes in
the Type I pinealocyte. The changes in the Type II pinealocytes with age were
mainly in nuclear shape and in the appearance of lipofuscin
granules.

The ultrastructure of the rat pineal stalk was
described. The pineal stalk contained few pinealocytes, glial cells and
numerous nerve fibers. The last were mostly non-myelinated axons, although a
few myelinated ones were also observed. Glial cells showed many filaments,
mostly in the processes which presented a longitudinal orientation. Other more
lamellar processes were found enclosing the axons. The pineal stalk became
wider as it reached the body of the gland. Ultrastructurally, this wide region
resembled more the pineal body. Bundles of non-myelinated nerve fibers were
seen around the pineal stalk.